console.log(Math.floor(4.5));//向下取整 4
console.log(Math.ceil(4.5));//向上取整 5
console.log(Math.round(4.5)); //四舍五入 5
console.log(Math.trunc(4.5));//截断 4
console.log(Math.pow(2,3)); //2的三次幂 8


console.log(Math.max(1,2,3)); //3
console.log(Math.min(1,2,3)); //1

console.log(Math.random()); //[0,1]区间

let num = Math.random() *100;
console.log(num);
//console.log(num.toFixed(2)); //num(number) ->Number对象


console.log();
console.log(parseInt("12.34px")); //12
console.log(parseFloat("12.34px"));//12.34
console.log(Number("12.43px")); //NaN
console.log(num);

console.log(num == NaN);  
console.log(isNaN(num));